Process of annealing sheet iron



PROCESS OF ANNEALING SHEET IRON May l, 1923.v

N W di Patented May l, 1923.

v J A.. or YoUNes'rowN, omo.

rnocnss or 'ANNE'ALIG SHEET mon.

pp licatiouled October 5, 1'921. Serial Nc.,505,541. l

To all lwhom it may concern.'

Be it known that'I, JAMEs'A. SMAU., a citizen ofthe United States, and a resident o f Youngstown, in the county of Mahoning and State of Ohio, have made a new and useful Invention in Process of Annealing' Sheet Iron, of which the following is a specification.

The invention relates to a process of annealing acks of sheet metal. It has for its principa objects the shortening of the present procedure, but more important, the provision of a process in the practice of which theproduct is better annealed, tougher and more free from defects such as stretcher strain and the like. The drawings'roughly indicate types of apparatus which may be employed,l although it will beunderstood that the-process is not restricted to use with any particular type of apparatus, or that a new l type of apparatus is required for its practice, the apparatus being shown merely to make the explanation simpler and more direct. In the drawings- Figure 1 shows in section a pack of plates in position in the annealing box. Fig. 2 is a section similar4 to that of Fig. 1 but with v other apparatus appliedto the box after its removal from the furnace, to facilitate the more rapid cooling ofthe pack. And Fig. 3'

is another section with a different means applied for cooling thefannealing box and its contents.

Referring to Fig. 1, the numeral 1 indi-` cates the annealing box, resting upon the base plate 2 with its lower edge embedded in the sand in the groove 3 in order to exclude .the air which would Aoxidize the metal durj ing the annealing process'. 4 is a pack of 40 plates which are to be ysubject to the annealing operation. l

Under the practice which has heretofore commonly prevailed, the annealingbox with its contents was placedin a furnace gradu- 46 ally raised through a'period ofseveral hours to a temperature of upwards 1450 F., and

after this maximum temperature was reached v it was maintained at this temperature forabout two hours, this periodl of the treatment 50 bein'gI known as soaking The furnace was then allowed to cool gradually durin a period'of several hours to a dark red or b ack 'heat approximating 800 or 900` F., after which the box was withdrawn from'the fur- 'nace and opened. The theory of operationv has been that the slow raising of the tempera? ture of the pack through the annealin period of from about 1200 F. to 1450 the slow cooling through such periodv was necessary to the securing cf toughness 'and freedom of defect in theproduct.

I have found `that a better product can be produced by a radically different procedure. According to my treatment, which maybe carried out in the same furnace and with the same" annealing box, the box and its contents f are vbrought as rapidly as possible u through the range from 1000o F. to 1400o or slightly thereabove and'is kept at such temperature only long enough to insure that all the sheets in the pack shall arrive at a fairly uniform temperature, after which the annealing box is immediately removed from the furnace and cooled-in the openair. I-

am of the opinion that the more `rapid the cooling through the critical range from 1450 F. to 1250'o 0r 1200 F., the better the product. The rapidity. of cooling ma be increased by artificial means such as t oseindicated in Figs. 2 and 3 although. the -invention is not limited to' use with either of ythose means or in fact with any means. v

In the arrangement of Fig. 2, the closure plugs 5, 5 are removed after the box is taken from the furnace, and the apparatus shown is applied for 'clrculatin'g a cooling, non-l oxidizing gas through the box to speed up AriENr "o1-Fries.

.and

the cooling of the pack. This apparatus comprises a circulating fan 6, piping?. and 8 and a cofoling chamber 9 through wh1ch the piping carryingthe circulating gas is passed and cooled in any desired way.

. In the arrangement of Fig. 3, the box 1 is I exposed after withdrawal from the furnace,

to a blast of air from the fan 10.

Various other expediente may be em.- ployed for facilitatin` the cooling of the box and its contents. or instance, the box might be allowed to remain in the furnace, and a cooling blast of air circulated into and through'the furnace to cool itand its contents down ata rapid rate.

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My theory as to the betterresults secured -by my Aimproved process and compared to lthe process commonly employed 1s that Ithe soaking process and the slow cooling during the critical period from about 1450 F. down to 1000 F. as practiced 1n the usual procedure promoted the formation of free or massive' cementite. which is a granular carbide formedby the union of the carbon in the iron lwith the iron itself.

its presence in the finishedproduct impairs its ductility and is conducive o f the lines known as "stretcher strain when the sheets are full finished. Y

With my process the annealing is accomplished during the rising temperature in the furnace from 1200" F. up to 1150o F. or somewhat higheizafter which time the rapid cooling tends to prevent the formation of coarse grained or massive cei'nentite, the carbide vwhich is formed during this more rapid cooling through the critical period being of the type known as peartite 4in which 'the structure consists of thin interspersed laminations of cementite and pure iron or ferrite.

This is' the most ductile form in which the cenientite can occur and it should be held in this form in so far as possible instead of being allowed to change into massive free form which increases the brittleness of the sheets and their liability to develop defects along the lines where the cementite occurs.

lt .will be understood that the term iron is usd in its generic sense to' niean iron or steel Ain the wide range of forms known as sheet iron or sheet steel; also that the temperatures specified are only roughly approximated.

What l claim is: v

l. A process of annealing a pack of iron sheets which consists in bringing the pack upjthrough an annealing temperature in an enclosed atmosphere. and then causing said pack to cool down rapidly while still closed off from the outside atmosphere.

Q. process of annealing a pack of iron sheets which 4consists in bringing the pack up through an annealing temperature ofy from 1200o F. to 1450O F. or upwards in an enclosed atmosphere and causing said pack to cool down rapidly through the same range f while still closed off vfrom the outside atmosphere. 3. A process of annealing a. pack of iron sheets which consists in bringing the pack up through an annealing temperature in an annealing box in* a furnace. then removing the box with its pack therein from the furnace while at the upper portion of the annealing range oftemperature and allowing the box and its contents to drop rapidly in temperature.

4. A process of annealing a'pack of iron sheets which consists in bringing the pack up through an annealing temperature in an annealing box in a furnace. then removing the box with its pack therein from the furnace. while at the upper portion of the anneahng range 'of temperature and.y allowing Y rIhis coarse `grained or massive cementite 1s relatively brittle and of low tenslle strength, so that the box andits contents to drop rapidly in temperature through the critical range of from 14500 F. down t-o 12000 F.

5. A process of annealing a pack of iron sheets which consistsin bringing the pack.

up through-an annealing temperature' of fronr1200O F. to 1-150O F'. and upward in an annealing box in a furnace, then removing the box with its pack therein from the furnace while at its upper range of temperature and allowing the box and its contents to drop rapidly in temperature of from approximately 11509 F. down.

6. A process of annealing a pack of iron sheets which consists in bringing the Apack up through an annealing temperature in an annealing box in a furnace, then removing the box with its pack therein from the furnace while at the upper portion of the annealing range of temperature and as soon as the entire pack has arrived at a unifc vn temperature, and allowing the box and its contents' to drop rapidly in temperature through the critical range from approxi matel 14150o F. down.

7 process of annealing a pack of iron sheets which consists in bringing the pack enclosed atmosphere, and then applying cooling means to the pack to cause said pack to cool down rapidly while still closed off from the outside atmosphere. i

9. A process of annealing a pack of iron sheets which consists in annealing the plates in arising temperature in an enclosed atmosphere, and then removing the application of heat to the pack while at its upper range of temperature and permitting the pack to cool rapidly while still closed O from the outside atmosphere.

l0. A process of annealing a pack of iron 'sheets which consists in annealing the plates in a rising temperature in an enclosed atmosphere in a furnace, and then removing the pack in its enclosed atmosphere from the furnace while the pack `is still at its upper range of temperature, and permitting the pack to cool rapidly while still closed ofi from the outside atmosphere.

11. A process of annealing a pack of iron sheets which consists in bringing the pack up through an annealing temperature in an annealing box in a furnace, then removing the box with its pack therein from the furnace while at the upper portion of the annealing range of temperature, and than Gooling the pack by passing a current of nonoxidizing gas ythrough the box.

12. A process of annealing a pack of iron sheets which consistsl in annealing the plates in a rising temperature ranging from 10000 F. to 14000 F. and upward in an enclosed atmosphere and then removing the application of heat to the pack While at its upper range of temperature, and permitting the pack to cool rapidly While still closed orf from the outside atmosphere. v v.

13. A process of annealing a pack of iron sheets which consists in annealing the plates in a rising temperature ranging from 10000 F. to 14000 F. and upward in an en,

closed atmosphere and then removing the application of heat to the pack While it is at its upper range of temperature, and permitting the pack to cool rapidly from a temperature of 14000 F. down to 10000 F .'While still closed olf from the loutside atmosphere:

. 14. A process of annealing a pack of iron sheets which consists in bringing the pack up through an annealing temperature of upwards of 10000 F. and then applying cooling means to cause the pack to cool down rapidly While still closed off from the outside atmosphere.

In testimony whereof, I have hereunto subscribed my name this 26th day of September, 1921.

JAMES A. SMAIL.

Witnesses:

GEORGE W. COVER, 

